Ortofon S-15T Vintage Stereo Cartridge

Ortofon S-15T cartridge, 1960's vintage, which came out of my father's system. Working condition unknown. The identifying model lettering has long since worn off, so I'm going by internet info to identify the model number. Also, it weighs in at 17-18 grams, which would lead to it being the internal transformer version. Stylus and diamond are intact, see pics, but I don't know if this is an elliptical diamond version.